Pulse jet engine havingf variable



April 20, 1954 w. TENNEY I 2,675,670 PULSE JET ENGINE HAVING VARIABLEINLET CONTROL Filed May 15, 1948 2 Sheets-Sheet 2 INVENTOR. lMLL/AM L.TZ-WNEY w a E Q u A z a m E w M m .5 7 x a MM m /m m B I g \Lf) E w W5 v6 4d m E I E 1 m7 M #w 7 E i ATTORNEYS Patented Apr. 20, 1954 UNITED.STATES PATENT OFFICE PULSE JET ENGINE VARIABLE" INLET CONTROL 4 Claims.

This invention relatesto pulse jet engines and more particularly tointake controls therefor. In jet engines of this character air isintroduced at the forward end of the engine into a com bustion chamberwhich may be merely a forward section of the jet tube. Fuel is likewiseintroduced into the combustion chamber or section and the combustiblefuel-air mixture is exploded therein. The resultant products ofcombustion and any augmentation air which may have been drawn into-theopen end of the exhaust tube are ejected forcibly from a rearwardly'extending tail pipe or jet nozzle and thus produce the thrust effort ofthe engine which serves to drive it and its load in a forward direction.

The frequency of the explosions in the unit depends primarily upon thelength and other physical dimensions of the combustion chamber-tailpipeassembly. In small engines suitable for the propulsion of modelairplanes, boats, cars and the like, the frequency of the explosions arein the. order of 200-300 cycles per second, whereas in larger units suchas are suitable for the propulsion of target airplanes, guided missilesand the like, the explosion frequency is lower.

The operation of pulse jet engines is exceedingly critical in that evenslight and almost negligible variations in the physical constants andoperating conditions cause substantial and largely unexplainedvariations in thrust, fuel consumption and the like. Such theory ashasbeen advanced to explainv such phenomena as (l) re-ignition withoutsustained external ignition apparatus, (2) frequency of explosion, (3)variation in thrust and fuel consumption with changes in speed andaltitude and. other factors, is largely speculative and for the mostpart unsubstantiated. Such progress as has been made is based primarilyon experimentation, using the trial and error method.

In my experiments it has been discovered that thrust, fuel economy andindeed, even the maintenance of the cyclic; explosive phenomena isconsiderably dependent upon the rate of intro-- duction of the aircomponent of the combustion mixture into the combustion chamber. Thus,utilizing a pulse jet engine of the general design described incopending applications Serial No. 649,882 filed February 25, 1946, nowPatentv No. 2,609,660, and Serial No. 661,280 filed April 11, 1946, nowPatent No.. 2,587,100, itlhas been found that when the unit is standingstill andv hence is not receiving any ram air, certain thrust andspecific fuel consumption are obtainable, yet

when the same unit is permitted to obtain an appreciable velocity or issubjected to variations in air pressure within the range of atmosphericvariations, relatively substantial decreases in thrust and fuel economyensue. The same phenomena hold true for larger size units which I have?tested. In extreme instances the effect of velocity and pressurevariations may be so pronounced that the unit ceases to function inthat.

cyclic operation does not continue. It has also been observed that asthe: velocity increases with wide open: intake, the zone of combustionas indicated by most pronounced heat liberation, shifts towards theexhaust end of the jet tubes.

In seeking to overcome these objections I have discovered. thattheconditionof maximum thrust and minimum specific fuel consumption canbe better maintained under varying conditions of velocity andatmospheric pressure (or altitude) by varying the restriction at the airintake throat, and it is an object of the invention to provide for suchvariation.

More specific objects of the invention include provision of mechanismsin pulse jet engines for adjusting the air intake for variousconditions; to provide-a pulse jet engine wherein the throatrestriction. is adjusted automatically in response to speed. or inresponse tothe joint action of speed and altitude and to provide animproved pulse jet engine having means for manually adjusting the airintake either at the intake itself by the use of variousforms ofrestrictions or remotely controlled.

Other and further objects of the invention are those: inherent in. theapparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings whereinFigure 1 is a sideview of a pulse jet engine, partly in section,showing; one form of adjustable intake;

Figure 2 is a side view of a pulse jet engine, partly in section,showing asecond form of ad, justable intake which is automaticallyresponsive to velocity;

Figure 3 is aside view of a pulse jet engine, partly in section, showinga third form of adjustable intake, which is capable of manual adsjustment";

Figure 4: is a side view of a pulse jet engine, partly section, showinga fourth form of adjustable intake which is automatically responsive tovariations velocity and altitude (barometric pressure-) Figure 5 is eside view of a pulse jet engine,

partly in section, showing another form of adjustable intake;

Figs. 6 and 7 are side views partly in section showing modified forms ofexhaust tube.

Throughout the drawings the combustion chamber and jet tube (or exhausttube, as it is sometimes designated) are foreshortened so as to afiord alarger scale for illustration of the intake end of the several engineswhich are the principal subject of the invention, but it will beunderstood that the combustion chamber and exhaust tube are ofappropriate length, suitable for the service involved. In use thedevices shown in the drawings produce a thrust and tend to move fromleft to right. The portion on the right in each figure is accordinglyreferred to as the forward end, portion or direction. The portion at theleft is the rear end, portion or direction.

Throughout the drawings corresponding numerals show corresponding parts.

Referring to the drawings the basic engine is illustrated in Figures 1through and consists of a combined combustion chamber and jet exhausttube 10 which is provided at H with a valve or valve bank of anysuitable design capable of permitting the flow of air or a fuel-airmixture therethrough cyclically according to valve operation and in thedirection indicated by the arrows l2. The valve bank Il may be of anysuitable design such as that illustrated in Patent No. 2,609,660, orapplication Serial No. 661,367 filed April 11, 1946, now-abandoned. Thevalve mechanism in the illustrative structure herein is shown as beingmounted in a bulkhead wall !3 and spaced from the interior surface ofthe combustion chamber and exhaust jet tube 10 so as to provide an areathrough which fuel jet nozzles 14 protrude. The nozzles M, of which aplurality are used, are oriented so as to provide a spray dischargetowards the central area downstream from the valve bank II, the spraydischarge of the nozzles being illustrated at I5. The fuel thusintroduced into the combustion chamber mixes with the infiowing airstream which enters through the valve bank II and provides an explosivemixture which is exploded cyclically in the operation of the device. Theplurality of nozzles I 4 are connected together by a ring header-tube 16which circumscribes the valve bank I I. At one point a fuel supply lineis connected to the ring, as indicated at l8. Fuel under pressure ispumped to the header ring l6 from an external supply.

Other fuel injection mechanisms, such as those illustrated in theaforesaid Patent No. 2,609,660,

may be utilized, if desired. Likewise one or more valve banks, such asthose illustrated in said application may be utilized at H.

The tube l0 not only forms the combustion chamber but also forms the jetexhaust tube of the device and may be of uniform diameter throughout ormay, if desired, have a larger diameter adjacent the valve bank as shownin Fig. 6 so as to form a combustion chamber which is then connected byan intermediate section of smaller diameter to the terminal end 20 whichmay, if desired, be flared as illustrated at 2|. The tube I0, ifdesired, may have a gradually increasing diameter towards the terminalend followed by a reverse curve similar to a wine goblet section asshown in Fig. 7 so as to provide for supersonic jet velocities of jetexhaust.

The intake section generally designated 22 has a smooth interior Venturicurved section 23 having a minimum diameter at 24 which is smoothly 4curved to the entering or nose section 25. The exterior surface 26 ispreferably kept as free as possible of protuberances so as to cut downparasitic drag where the unit is used in free flight as in a guidedmissile, but where the unit is housed the housing is shaped so as toprovide the least parasitic drag. This much of the construction isuniform throughout the various figures in the drawings.

In the operation of a device of this character air enters at the forwardend 25 at a velocity depending upon the engine design and condition ofoperation, as well as the forward motion of the unit. After enteringthrough the Venturi nozzle 24 the air or fuel-air mixture, in the eventthe fuel is introduced in the nozzle section 22, impinges upon the valvebank II or other suitable inlet section and passes into the combustionsection which is the portion of tube 10 immediately downstream from thevalve bank I I. Initially ignition is accomplished from an externalsource such as by means of a spark plug 28. As soon as the combustiblemixture is ignited the pressure developed in the combustion zone forcesthe products of combustion in the forward portion of the tube and thefresh air mass in the rear portion of the tube rearwardly through thetube I0 and out of the terminal end 20 as indicated by the arrows 29.The explosion likewise causes the valves of the valve bank II to closeuntil the pressure of the explosion has subsided. Even when the unit 22is static, that is to say it has no forward velocity, the rearward flowor mass action of the gases moving in the direction of arrows 29produces what is apparently a negative pressure condition in thecombustion zone (to the left of the valve bank I l as shown in thefigures), and this causes a fresh flow of air or airfuel mixture to bedrawn through the valve bank I! whereupon the second explosion occurs. Anegative pressure also occurs at the rear end of tube l0, causing a flowof fresh air back into the rear portion of the tube through the terminalend 20. This action is repeated cyclically and soon after operationbegins the high tension supply to the spark plug 28 is interrupted andre-ignition occurs thereafter due to the inherent functioning of theapparatus. The zone of most intense heating is somewhat removed to theleft from the valve bank I I, since the fresh inflow of air or fuel-airmixture through the valve bank ll serves to cool the valve bank andsomewhat to lower the temperature of the region immediately adjacentthereto, and the cyclic fresh air influx through the terminal end 20tends to cool the region adjacent thereto.

When the device is moving rapidly through the atmosphere the air flowthrough the venturi 24 increases due to the ram air effect, and it hasbeen observed that the zone of most intense heating or combustion movesfarther and farther away from the valve bank towards the outlet of thejet tube 26 as the ram air effect increases. A decrease in barometricpressure has an opposite eifect for while the velocity of the incomingair flow may be increased the decrease in barometric pressure has theeffect of decreasing the incoming mass of air. Therefore, to some extentan increase in velocity is counterbalanced by a decrease in barometricpressure, though not in equally compensating amounts.

As the ram air or velocity effect increases the thrust afforded by theengine decreases and the specific fuel consumption, in pounds of fuelper pound of thrust per hour, increases. I havediscovered that byvalving he Ven tufi tube section 24, this decrease in thrust andincrease in *iZue'l consumption can be partially or completelycounteracted, depending upon other -operating conditions and details ofengine designand as a result the unit prov-ides improved thrust and fuelecononly as-oompared with previous pulse gle't engines.

In Figure 1 the Venturi section is provided with a'frame composed of twoor more forwardly and inwardly curved struts 3% which are joinedtogether by a streamlined nose section 3| which serves as a centralsupport for the forward end of the rod 32, the rear end 33 of whichis'attached to the valve ban-x. Upon the rod-there is mounted an objectwhich has a streamlinedsur-faceSpresenting the comparatively blunt-noseportion 34, a maximum diameter section 35 and the long tapered endsection 3%. This object generally designated. 37, which may be termed aVenturi flow restrictor, is mounted so as to be-movable forward or backupon the rod 32 and since the rod 32 is mounted at the longitudinal axisof the Venturi section 2-4, the flow restrictor 3! may thus be adjustedso as to be at any 'posi. tion from the forward (least restricting)position shown by dotted'lines 37 to the rearward (most restricting)position shown in full lines. In the forward position the blunt nosesection 34 fits neatly within the correspondingly curved surface 3% ofthe central nose '31. The flow 'restrictor is provided with one or moreset screws or other fastening devices at 39 by'which its position may befixed by manual adjustment so as to be located anywhere along the rod32. In this form of the invention the restrictor is adjusted at anyposition so as to provide maximum thrust and minimum fuel consumptionfor any desired speed or barometic operating conditions.

Referring to Figure 2 there is illustrated another formof the device ofgenerally similar construction except that in this form the flowrestrictor, generally designated 40, is mounted so as to beautomatically movable between 'fixed least-restricting andmost-restricting positions with reference to the Venturi section 2t.flow 'restrict'or to is internally boredat II and is provided with a webat 2 having an aperture therein sized so as to slide neatly upon the'rod '32. The front end of the bore l'l'is provided with a screw-in plug43 which is likewise apertured so as to slide upon the rod 32. The rearend of the restrictor 46 has bore '44 in which the long cylindrical stopmember 65, which is fixed to the rod .32 by means of set screw 46, isadapted to slide. The member 65 is fixed upon the shaft 32 and therestrictor iii slides thereon from the position shown in full lines tothe position shown in dotted lines. It will be noted that in the dottedline position the trailing edge 41 of the restrictor is still supportedon the forward end 48 of the stop member 45. When the web 42 is againstthe front end of the stop member 45, the flow restrictor 50 is in themost restricting position. Upon the rod 32 there is provided a collar5'6 which is held in any adjusted position on the rod by means of a setscrew 5|. The collar 50 serves as a stop. for the spring 52, the forwardend of which pushes against the screwin plug #3. Spring 52 is showncompressed in Figure 2 and the force exerted by it upon the plug 43 isin the forward direction. Thus, the spring 52 naturally tends to expandand to force the entire flow restrictor Ali to the forward or dottedline position til, in which the flow restrictor resides when the devicei in static con- The acme-to dition. In this pesi tion thenumoer Wt 'isfinfth least-restricting condition.

As velocity of the engine increases the ram air pressure exerted upon"the forward end of the flow restrictor Ml, indicated by the arrows =51,gradually increases "until it is sulii'cierrt to over come the force-ofspring 52 and a the velocity increases the' flow restrictor M1 isgradually pushed back until it reaches "the position shown in full iinesin which a maximum restricting edect thej fiow'through ti-re 'ventur i23 is achieved. will be noted passing the force exerted by the ram airupon the flow restrictorlll decreases as the barometric pressuredecreases (clue to the lesser density of the air) while the forceproducedin the direction of arrows at increases for increases ofvelocity. Decrease in'barometric pressure as is occasioned by highaltitudgffli partially *but not entirely compensates the mcrease invelocity. The position 'of member l'il moves to compensate for variationin speed and barometric "pressure -=during operation. Referring toFigure 3 there is illustrated "a device corresponding to that shown in"l ligure 2, except that the underside of the "flow restrictor notchedat 56 to receive an actuating link 51-wh=ich is 'connectedto the flow'restr'ictor by the pivot-pin 5B. The 'rear end of the actuating link ispivotally connected at 5-9 to the lever cue men extends through a slot"6| in the-sideof the venturi *22, the lever 60 being pivoted at 62 'to'-the Venturi'inlet structure. At 63 there is illustrated a housing whichmay be part of the air 'r'ciilor other structure into which the engineunit is built and upon this portion of "the device there is mounted apull wire control bracket "64 which serves to hold the housing "65 ofthe pull wire which extends to a remote operating station '6'6. Anoperator control 6"! is connected to "the wire 68 that extends throughthe housing 65 and is Divotally connected at 69 to the lever 69. Bymovement of the operator control 67 in therearward direction, asindicated by the arrow f'l'll, the restrictor can thus be moved in theforward direction for static operation or operation at low velocities.As the velocity increases DI" when other'conditions require anadjustment of the now through "the venturi 22, the operator control '6"!is pulled 'or pushed and the flow restri'ctor .4? is accordingly movedto "any desired position from fully open (unrestricted flow conditionsshown at 40') to the maximum restriction position shown in full linesin'Fig'ure 3. I In Figure 4 the apparatus of Figure 3 is shownslightlymodified in that a greater range of motion is provided for the'flow restrictor 4-0. This is'afiorded by extending the braces 30A to amore forward position so as to provide a longer rod 32A on'which theflow restrictor is adapted to slide. The movement of the flow restrictori!)- is of the same type as that described with reference to Figure 3,"but the range is greater, this being alforded by the lever 60A whichis-mountedupon a bracket H extending outwardly from the outer surface ofthe "Venturi nozzle section '22. f The length of the s'lotBiA, link51A1w'hich is pivoted to both the flow'restrictor and to the lever 60A,and the length of thelever 60A are all proportioned accordingly. As aresult the flow restrictor may be moved from the least-restrictingposition shown in dotted lines to the position of maximum restriction ofthe Venturi tube shown in full lines.

The full range of movement is accomplished by means of a mechanismgenerally designated 72'whlch is automaticallyresponsive to velocity andbarometric pressure changes. Thus, within the housing 13 shown in dottedlines merelyas representative, upon which the engine unit is mounted,there is provided a bracket 14 having an annular bellows chamber 15which is con nected by the tube 83 to an open-ended air inlet funnel 81.The bellows section '15 is closed at its forward end by the plate 15 towhich there is likewise attached the forward end of a baroe metricSylphon bellows containing a puregas 11. The rear end 18 of thebarometric Sylphon bellows 11 is pivotally attached at 19' to; -alever-80 which is pivoted at 8| to the bracket 82 on the unit 13. Theupper end of the lever 80 which is a motion multiplying lever isattached at 84 to a link 85 which is pivotally attached at- 86 to thelower end of the leverBOA. A spring 89 is attached to the mounting panel14' andto the pivot 86 and accordingly tends to pull-the link 88 and thelower end of lever 60A in the rearward direction as indicated by thearrow 89. This tends to push the flow restrictor 40 to the dotted lineposition. If it is assumed that the flow restrictor is in anintermediate positiondue to a steady pressure exerted through tube 93;upon the interior of annular bellows section 15, then the effect of adecrease in barometric pressure will be to expand the bellows TI and topush the lever 80 in the direction of arrow 90. This tends to push theflow restrictor 40 toward the dotted line position. If the velocity ofthe unit increases greater pressure is exerted in the direction ofarrows 90, and this tends to increase the (ii: mension W of the annularbellows section 1 5. This has the effect of pulling the lever in thedirection of arrow 9! and tends to move the flow restrictor 40 towardthe full line position. If desired, a servomotor system may beincorporated in the linkage between the actuator '12 and the flowrestrictor 40 so as to increase the power for moving the flowrestrictor, particu larly in larger size units. A

In Figure the Venturi nozzle section 22 an the remaining portions of theengine are equipped with two or more forwardly extending ribs 92 whichconverge together at 93 and serveas a support for the forward end of therod 3213. Upon the rod there is mounted a flow restrictor generallydesignated 100 which has a smoothly: curved converging forward end 94and a fiat planar or undercut trailing edge 95. This flow restrictor maybe undercut as shown by the 'dotted' lines 96 so as to reduce weight.The flow restrictor is provided with a set screw 91 by means of which itmay be adjusted in any position from the forward full line position to aposition closer to the nose 25 of the venturi. When the flow restrictoris in the forward or full line position shown Figure 5, the air flowtherearound is as indicated by the full line arrows l0l. When the flowrestrictor is in a position more closely adjacent the nose 25 and theventuri 22, the flow is restricted to a greater degree and is in thedirection of the dotted line arrows I02. Any degree of restriction maythus be achieved'by adjusting the position of the flow restrictor I00. I

As many apparently widely different embodi- '8 ments' of this inventionmaybe-made without departing from the spirit and scope thereof, '-it isto be understood that I do not limit myself to the specific embodimentsherein. 7

What I claim is: r e

1. A resonant pulse jet engine having a combustion zone enclosure withinterior walls constructed for the rapid pulsating flow of gasestherethrough and asubstantially unrestricted jet exhaust tube emanatingtherefrom and having a cross section not substantially less than thatofthe adjacent end of said combustion chamber, said engine also havingan automatic valve operable by and in direct timed relation with theresonating pulsations of said engine, a Venturi shaped inlet into saidcombustion zone enclosure, said inlet being orientated to face in theopposite direction from said jet exhaust tube, said automatic valvebeing located in said inlet passage, means for introducing air and fuelinto said combustion zone enclosure for resonant periodic selfsustainingcombustion within said combustion chamber and said exhaust tube, aninlet passage restrictor in the shape of an air foil surface ofrevolution closed to the passage of air therethrough, means mountingsaid restrictor substantially coaxially of the Venturi inlet passage andfor movement to varying positions with refer-- ence to the end of saidpassage for varying the restriction to air flow through said passage tocontrol the quantity of air supplied to said engine to maintain saidself-sustaining combustion therein under varying conditions, and meansnormal- 1y biasing the movement of said restrictor to a position leastrestricting said Venturi passage.

2. The apparatus of claim 1 further characterized in that stops areprovided on the means mounting the passage restrictor for limiting itsmovement at positions of selected minimum and maximum restriction ofsaid Venturi passage.

3. The apparatus of claim 2 further characterized in that said passagerestrictor is mounted for movement under the effect of ram air impingingthereon and said means for biasing has an inherent strength insufficientto maintain said passagerestrictor in the least restricting positionwhen the ram air pressure reaches a predetermined amount.

4. The apparatus of claim 1 further characterized in that means isprovided connecting said passage restrictor to a remote control formanually varying the position of said passage restrictor from saidremote station.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1 2,142,601 Bleecker Jan. 3, 1939 2,390,161 Mercier Dec. 4,1945 2,396,598 Neumann et al Mar. 12, 1946 2,489,953 Burney Nov. 29,1949 2,570,629 Anxionnaz et a1 Oct. 9, 1951 FOREIGN PATENTS NumberCountry Date 50,033 France Aug. 1, 1939 Addition to No. 779,655

